The Firefox OS will land in a crowded environment, where many small operating systems are trying to become the "third eco-system," alongside Apple's iOS and Google's Android. Together, those two account for 91 percent of smartphone sales, according to research firm IDC.

Mozilla has an ally in phone companies, who are interested in seeing an alternative to Apple and Google. Thirteen phone companies around the world have committed to supporting Firefox phones, Mozilla says, including Sprint Nextel in the U.S. Phones are expected this summer in countries like Brazil, Colombia, Mexico, Poland, and Spain.